/**
* Returns the global worker pool for the current context.
*
* @param PoolInterface|null $pool A worker pool instance.
*
* @return PoolInterface The global worker pool instance.
*/
function pool(PoolInterface $pool = null)
{
static $instance;
if (null !== $pool) {
$instance = $pool;
} elseif (null === $instance) {
$instance = new Pool();
}
if (!$instance->isRunning()) {
$instance->start();
}
return $instance;
}
